I have a set of 4 pcs 8874 tubes for sale. These are out of my Alpha 76pa
3-hole tube amp.
They still have plenty of output but they are far from spring chickens.
Performance measured below so you can see what I’m seeing here on the bench.
If you are interested in these tubes, contact me offline (jeff @ ac0c.com).
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
The tubes are late 80’s vintage and may be the originals. In the time I have
had the amp, the amp was run at about 1KW out of respect for the amp’s age and
the high cost of replacement tubes. Shortly after I got the amp (3 years ago?)
I put in grid protection circuitry and an additional fan.
http://www.ac0c.com/main/page_homebrew_alpha_76pa_mods.html
Data from the 3 tubes now in the amp:
BAND Ip B+ Po Ig
-----------------------------------------------------------------------
80m 930 mA 2150V 1330w 40 mA
20m 880 mA 2200V 1320w 53 mA
10m 920 mA 2150V 1160w 35 mA
10m 690 mA 2200V 900w 28 mA
Po measured with LP100A feeding a dummy load.
Ip/B+/Ig read from 76pa meter
Drive power was 80-90w for the first 3 runs; the last 10m (900w) where the
drive power was 39w.
The 4th tube has similar good output but the amp would glitch from time to time
with it. I’m not sure this was a tube problem as there was a PS relay that had
burnt contacts which I replaced about the same time.
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